Process and apparatus for the treatment of waste sulfuric acid



0 United States Patent on 3,545,519

[ lnvemm's Koichi Kawamura References Cited lchihm'm UNlTED STATES PATENTS Miyoshi lshikawa, Sakai-shi, and Teruji I 6] l 534 I2 926 Yoshii, Takatsuki-shi, Sigehiko Sugiyama, '044 K'afft 3/ 1 72 Kobeshi, and Hiroshi Kato, 0saka,.lapan 3/1956 Ashley 23/302 2,078,088 4/1937 Mantius eta]. 23/306 l2l] Appl. No. 845,438

2,750,894 6/1956 Thomas et al. l03/l 1 1X [22] PM 1969 a 294 650 12/1966 M r Patented Dec n a anteu 8|. [73] Assignees Maruzen Oil Company, Ltd., FOREIGN PATENTS Osaka, Japan, and Kimura Kakoki 941,746 1 1/1963 Great Britain 23/l 72 Co., Ltd., Amagasaki-shi,.lapan, 309,834 4/1929 Great Britain 23/ l 72 3 corporatlon Japan Primary Examiner- Norman Yudkoff Priomy g- 8 Assistant Examiner-J. Sofer J p Attorney- Karl W. F locks [31 No. 43/55631 [54] PROCESS AND APPARATUS FOR THE ABSTRACT: A rocess and a araltus for continuous] TREATMENT OF WASTE SULFUR: recovering sulfuric acid in a high oncentration of 75 to 8% 4 Claims 1 Drawing percent by weight from a waste sulfuric acid which has been [52] US. Cl. 159/17, used as a catalyst. solvent or dehydrating agent in various 0rl59/20. l59/47: 137/567 ganic synthetic reactions in the field of petroleum and chemi- [5l] Int. Cl. Bold 1/26, cal industries. The process comprises filtering off the impuri- 801d l/l00 ties from the waste sulfuric acid, degassing and subsequently [50] Field of Search 23/274, forcing the waste sulfuric acid to successively flow into a 276, 307, 306, 167, 172; i597] 7, (Dec.), (acid), 47,47(WL), 20; 103/] 1 KB); 203/12; 137/567 LEAD HOMOGEN BRICK LIQUID CIRCUITS APPROX. 98% H2504 H,SO -sealed system, followed by a stepwise vacuum concentration.

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omodmmzw mtInzmw N i v 823 vw mmmmzm INVENTOR5 KOICHI KAWAMURA MIYOSHI ISHIKAWA TERUJI YOSHH SIGEHIKO SUGIYAMA HIROSHI KATO S ROCKS ATTORNEY PROCESS AND APPARATUS FOR THE TREATMENT F WASTE SULFURIC ACID This invention relates to a process and apparatus for the recovery ofwaste sulfuric acid. More particularly, this invention relates to the recovery of sulfuric acid from a waste liquid from the various processes in the field of petroleum and chemical industries. v

Regarding the concentration of sulfuric acid to a high degree, only the following processes have heretofore been known as seen from Ryusan Kogyo Binran (Handbook of Sulfuric Acid Industry) published in 1951.

, l. Sulfuric acid concentration by the Pauling process (A sulfuric acid concentration vessel is employed.)

2. Cascade type sulfuric acid concentration (The sulfuric acid, which drops into a dish or beaker, is countercurrently heated from below.)

3. Chemico Drum type sulfuric acid concentration (A large quantity of hot gas heated to 600 to 700 C. is blown directly onto the surface of liquid.)

4. Simonson-Mantius vacuum concentration (The liquid is collected in an evaporator and subjected to evaporation in vacuo.)

All of these conventional processes as mentioned above are carried out by batch type,.rather than continuous, operations.

operations and are extremely inefficient. In addition, due to sulfuric acid sludge produced from organic synthesis, and impurities other than sulfuric acid, e.g. unaltered raw materials, there is a great difficulty in selecting economical and anticorrosive materials. There are also the faults that heat efficiency is extremely low, and the apparatus is damaged in a short time due to corrosion therefore efficiency is rapidly decreased.

Sulfuric acid of high concentration of 75 to 85 percent by weight is used in various organic synthetic reaction in the field of petroleum and chemical industries. For example, such concentrated sulfuric acid is used as a catalyst or solvent in reactions such as hydration of an olefin (in which propylene, butylene, isobutylene, amylene or the like is absorbed by sulfuric acid and the resulting product is hydrolyzed); carboxylation of an olefin, alcohol, paraffin, ester, ether, mercaptan or the like (in which an olefin or the like is reacted with carbon monoxide in the presence of sulfuric acid and the resulting product is diluted with water); separation of a xylene isomer from xylene mixtures (in which for example, only m-xylene in the mixtures is selectively sulfonated with sulfuric acid followed by separation of the resulting product, whereupon the separated product is hydrolyzed to separate m-xylene); decomposition of cumene hydroperoxide (in which the decomposition is conducted in sulfuric acid); p lymerization ofolefins (in which, for example, isobutylene is polymerized in the presence of sulfuric acid); and alkylation by reacting an olefin with a paraffin, benzene or the like (in which, for example, isobutane is reacted with olefin in the presence of sulfuric acid to produce gasoline; or olefin is reacted with benzene to produce alkylbenzene). In addition, concentrated sulfuric acid is widely used as a treating agent for the refining of petroleum fractions and as a dehydrating or drying agent. The waste sulfuric acid from the various uses as mentioned above contain impurities, such as acid sludge, polymers, reaction products or the like.

The aforementioned conventional batch processes for the concentration of sulfuric acid are, furthermore, not always adaptable to the treatment of the waste sulfuric acid obtained from various organic synthetic reactions in the field of petroleum and chemical industries.

This invention resides ina new and novel process and apparatus for continuously recovering for reuse concentrated sulfuric acid from waste liquid containing impure sulfuric acid. The present invention is principally directed to start from such waste liquid containing acid sludge and organic carbonaceous materials, as impurities.

It is an object of the present invention to provide an improved sulfuric acid recovery operation which overcomes defects of the prior art, such as indicated above.

The accompanying drawing is a schematic flow diagram of a preferred example of a system which is suitable for carrying out the present invention.

Referring to the drawing; a waste sulfuric acid which is obtained in the petroleum and chemical industries and has a concentration of 30 to 40 percent by weight is passed through an appropriate filter l,'such as an Oliver filter, in which solid impurities including the acid sludge, polymers, reaction products.

or the like are removed by filtration.

After removing the impurities the liquid is withdrawn via a line 31 into a filtrate reservoir 29. The collected filtrate is passed through a line 32 by-the action of a pump 30, and then through a line 21 into a rubber lined evaporator 2, here designated as the evaporator of a second effective vessel system. The top of the evaporatorZ communicates .with a condenser 14 through a line 27, adevice 12 for preventing countercurrent flow and a line 27. Owing to the condensing action of cooled water which enters the condenser 14 from a duct 33 as well as the sucking action of an ejector 15, the pressure in the interior of the evaporator 2 is reduced to 20 to 50 mmHg.

The evaporator 2 is provided with a circulative heating channel which comprises a line 34, a circulation forcing pump 4, a line 34, a multipipe type heating vessel 3 having a heat transferring surface made of impervious graphite and a line.

34". The liquid passed into the evaporator 2 is heated to about 5560 C..while. circulating through the circulative heating channel and is thereby concentrated to a sulfuric acid concentration of 45 to 50 percent by weight in such evaporator 2. Under these conditions, the usual lowering of efficiency which is due to the adhesion of scales and the corrosion does not occur, even when the evaporator 2 is lined with rubber and the heat transferring surface of the heating vessel 3 is made of impervious graphite.

The vapor evolved in the evaporator 2 is accompanied by the impure gases evolved from the liquid by the reduced pressure operation. These impure gases, which are condensed to liquid in the condenser 14, are withdrawn through the line 27, the countercurrent preventing means 12 and the line 27" to discharge lines 40. The uncondensed gases are sucked and discharged by means of the ejector 15. The provision of the countercurrent preventing means 12 between the evaporator 2 and the condenser 14 can prevent the countercurrent flow of the cooled water from the condenser 14 which is caused by the fluctuation of the operation condition. Thus, the danger thatthe cooled water would violently react with the sulfuric acid retained in the evaporator 2 to evolve reaction heat, thereby causing the damage of the apparatus is avoided. As a a result, the safe operation of the system is insured.

After being degassed and concentrated in the evaporator, the sulfuric acid liquid is passed through a line 22, a pump 5 and a line 22' to a first effect vessel system. The first effect vessel system consists of a lead homogen bricklined evaporator 6 and a circulative heating channel comprising a line 35, a circulation forcing pump 8, a line 35', a multipipe type heating vessel 7 having a heat transferring surface made of impervious graphite, and a line 35".

The liquid passed to the first effect vessel system is heated while circulating through the line 35, the pump 8, the line 35 the heating vessel 7 and the evaporator 6, and gases therefrom are evaporated in the evaporator 6. The heating vessel 7 is heated by live steam led through a line 26. the evolved vapor from the evaporation 6 is led through a line 24 and is used as a heating vapor for the heating vessel 3; here to the vapor is condensed and the liquid is discharged through a line 41. Such condensation causes the pressure in the interior of the evaporator 6 to be reduced to 350 to 400 mmHg and, at the same time, the sulfuric acid liquid is heated to 1 10 to 120 C. and concentrated to 60 to 65 percent by weight. In this instance, the evolved vapor is no longer accompanied by impure tort6, the evolved vaporis sufficientlyutilized as a heat source for the hjeating vessel'3in which the. temperature is 55to 60 C. Under the above rnehtioned temperature and concentration condition, the lead homogen bricklining of the evaporator 6 as well as the impervious graphite-made. heat transferring surface of the heating vesselisallowable. in this case, there is almost no possibility of the occurence of adhesionof scales as well as thecorrosion in the heating vessel.

The liquid concentrated in the evaporator .6 is subsequently led through a line 23 toa liquid fihishing system whichconsists circulatively of eva hio rator 9 of w hich the idegree of vacuum is regulated to to 50 mmHg, a .line 3 6, a'circulation forcing pump 111,21 line36',a multipipe type heating-vessel 10 1 and ttlitt'e 36?. Theliqui d passed to the. system is concentrated therin to 7585 p'ercelrithy weight and heated to 120 to 150 C. Theheating vessel :10 is heated by livesteam led through a line 2'16". ln this case, owing to the temperature (and concentration conditions asmenti'oned above, the evaporator 9 may be lined vvit h a cast iron havi g a high siljcon content, and the heating vessel ll) may have a hea't transferring surface made of impervious graphite which can housed without danger of occurence of adhesion ofscalesas well as corrosion'under these discharged by the action of a pump 19 through lines and 25 i nto a cooler 2t) in, which the concentratedliquid iscooled to about to C so that it may be continuously reused. According to the presei t invention, the sealing liquid portions of the mechas'e'als, of the pumps 4, 5,8 and 11 are pro- Y vided with an airtight circulationchannelfor, highconcentra tion, sulfuric acid (about, 98 pereent).. Stated; illustratively, there is a sealing liquid. circulation channel consisting of the a pump 8, a line 37, a sealing liquid bed tank v.16, anl ine'38, a pump 17, a line 38",a sealing liquid coolert l8 and a line39.

, Besides, there is a channel consistingof the line37, theline and a branched lin e 39 the pump 4 and a branched line 7 67"; channel consisting of the lines"?! an,d,;39,a lin'e 39'.', the pump '5 and'aliiie 37 ;anda'channel consisting of thelines 37 and '39,, a line 39', the pump andaline 37"".

As stated above, substantially all gases, are previously i ernoved beforethe waste sulfuricacid solution is subjectedto evaporation treatment. The'gases producecorrosive materials .at high'temperature. Therefor, thereis no danger of evolving undesirable gasses in the subsequent processing. Thepresent process is carried out at temperature, such as under 150 [c. T herefore, the evaporators have only. a to beline d with I economical materials specified above and the multipipe type "heatiiig vessel s mayhave heat transferring surfaces. made of economical material i.e impervious graphite.

' Enforced circulation is needed, because a .high concentration of sulfuric acid containing material is used; By suchcirculationjlittle scale is depositedon the heat transferring surface and nodrop'is causedirt heat transferring efficiency. f In the apparatus of this invention pumps are employed to v providejjth vacuum .system, nd a al of the mechaseals in theva cuum 'sy'steni is -effected fr e sealing liquidside to the circulating liquid side. If water were employedas a sealing liquid, there would be danger that the water would leak torthe ng liquid 'side :t he 'eby tending to causenot only the jentmaterial. of the mechaseal. portion he explo on in th'e pump jn .order to avoidsuch the present ihvehtion, there is employed q t i gforxampl P e a y, even wheh a leak. of the mechaseal ration sulfuric acid is mixedinto the mor theevaporationconcentrating sys ln AIS cas'e,.the eactionrheat is extremely small. Therefore there snag n tod amage the constituent materialso'ft chaseal andpurnp. Furthermore, it is noted v passedto-theliquid finishing system, in which theconcentrathat there is nodanger. to the exterior because, asaisealing liquid of the mechaseal portions, ahigh concentration' sulfuric acid iscirculated in an airtightmanne'r. Moreover, since the concentration is recognized'to be approximately constant, it is unnecessary to particularly increase the amount used.

1 -:'EXAMPLE An effluent waste liquid, obtained from the bottom of the v.stipper for separating the product from sulfuric acid in the process. for the preparation of secondary butyl alcohol vvherein ;b utylene is. absorbed by. sulfuric acidfollowed by hydrolysis, was subjected to thetreatmeritfl he effluent waste about 2 percent by weight of C -p0lymer hydrocarbon. The

liquid contained 38 percent by weight of sulfuric acid and waste liquid was filtered ata rate of l l,050 Kg/hr. toremove Ccpolymer hydrocarbon and the other solid impurities. Subsequently, the;waste liquid... was continuously passed to' the second effect vessel system inwhichthe waste liquid was'subjected to evaporation, ln--this instance, by regulating the degree of vacuum in theevaporator 2 to 50 mmHgtthe waste .was concentratedto 50 percent by wi'ghtsulfuric acid having atemperature of .60 C. The evaporatedamount was 2,650

2 Kg/hr.,,andthe-secondary'butyl alcohol dissolved in the waste 1 liquid,wassimultaneouslyliberated. Under such condition as ,,mentioned'- .above, the inner surface of the rubberline'd evaporator- 2 and theimpervious graphite-made heat transfer- 30* ringsurface of the heating vessel 3 .stood long-period use \vithout any corrosion. As ,the circulation forcing pump 4 was used, any adhesion of scale to the .heat transferring surface was not observed is longperiod and heat transfer ,was'e'ffec- -tive. Moreover,- byrsealin'g 98 percent sulfuric acid in the pump 4,,the'rewas no danger due to theleak of the sealing liquid.

Subsequentl'y,.,the firstly concentrated liquid was. continuously; passed ata rate of 8,400fKg/hr. To the first effect vessel,

system, inwhichthe concentrationwas effected at'a degree of vacuumof 375, mmHg to obtain a concentrated liquid having a 1 temperature of 1 20 C. and-a sulfuric acid concentration of'60 percent by weight. The evaporated amount was l-,400.,Kg/hr. Under such condition as mentioned above,- the inner surface of the leadhomo'gen bricklined evaporator 6 and the imperviou'sgraphite-madeheat transferring surface of theheating i'lessel' 7 stood long-period use .without any corrosion. As the cir- .,culation forcing .pump'8 wasemployed any adhesion of scale to :.the.-heat* transferringsurfacewas not observedin longperiod and; heat transfer ,was effective. Moreover, by sealing 9.8 percent-sulfuric acid in the pump 8,-ther'e .was no danger aconcentrated liquid: having a temperature of 128 C; aii'da 7 due to the leak'of the sealing liquid.

1 Asthe evolved vapor-fromthe evaporator 6 was-not accompanied by impure gases, the evolvedvapor was utilized as a 1 heating vapor-for the heating vessel 3 of the first concentrating system in which the operation was conducted at a temperature .lowerthan that'of the evaporator 6, without anydanger of corrosion-bfthe heat transferring surface.

v.Afterthe second concentratiomthe liquid was continuously tion was effected at a degreeofvacuum of-SOmmHg to'obtain sulfuricacid concentration ,of percent by weight; Under such condition 8S zlllllll0fl8d above, the inner'surface' -of the I -,high silicon contenticast iron. made evaporator'll and the imp'ervious graphite-made heat transferringsurface of- .the lheat ipgwesselilil stood longperiod use. without any corrosion. As the circulation forcingpump l luwas employed,-any.-:adhesion c of scale to the. heat transferringqsurface'wasifotrobservd for .long. period land-heat transfer'effciency was-kept iconstant Moreover, byseaIing 98 percent. sulfuric acid in the pump 1 l;

,there was no danger due tothe leak of the sealing-liquid.

The finished liquid, obtained at the rate of szso-x /hrq-was cooled to 40 C. intlie cooler 20, and continuously reused;

We claim:

l. A process for the treatment of a waste sulfuric acid ob tained in the petroleum and chemical industries which comprises:

continuously filtering solid matters from the waste sulfuric acid; continuously concentrating the waste sulfuric acid to a sulfuric acid concentration of 45 to 50 percent by weight under a reduced pressure of to 50 mmHg, while simultaneously removing volatile matters by degassing; further continuously concentrating the resulting 45-50 percent concentrated waste sulfuric acid to a sulfuric acid concentration of 60 to 65 percent by weight under a reduced pressure of 350 to 400 mrnHg; and and still further continuously concentrating the resulting 60-65 percent concentrated waste sulfuric acid to a sulfuric acid concentration of 75 to 85 percent by weight under a reduced pressure of 20 to 50 mmHg. c 2. An apparatus for the treatment of a waste sulfuric acid which comprises a filter; means to heat and concentrate the filtrate downstream from said filter comprising a second effect vessel system including a circulation'channel consisting of a rubberlined evaporator, means to reduce the inner pressure to 20 to 50 mmHg, a circulation forcing pump with a mechaseal having a high concentration sulfuric acid as a sealing liquid and a multipipe type heating vessel having a heat transferring surface made of an impervious graphite; means to further heat and concentrate said filtrate downstream from said second effect vessel system comprising a first effect vessel system including a circulation channel consisting of a lead homogen bricklined evaporator, means to reduce pressure therein to 350 to 400 mmHg, a circulation forcing pump with a mechaseal having a high concentration sulfuric acid as a sealing liquid and a multipipe type heating vessel having a heat itransferring surface made of an impervious graphite; means to high concentration sulfuric acid as a sealing liquid and a multipipe type heating vessel having a heat transferring surface made of an impervious graphite; and a cooler.

3. An apparatus as claimed in claim 2, wherein the mechaseal portion of the circulation forcing pump is provided with a circulation channel for high concentration sulfuric acid.

4. An apparatus as claimed in claim 2, wherein a countercurrent preventing means in is provided intermediately between the evaporator and a condenser. 

